1. Department of Occupational Health, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
2. Department of Occupational Health, School of Public Health, Shahid Beheshti University of Medical Sciences, Tehran, Iran
3. Infectious Disease Research Center, Golestan University of Medical Sciences, Gorgan, Iran
4. Department of Microbiology, Golestan University of Medical Sciences, Gorgan, Iran
5. Department of Occupational Health, Tehran University of Medical Sciences, Tehran, Iran